The present invention relates generally to cartilaginous reconstruction and more specifically to a method of forming a reconstructive structure for cartilage elements, reconstructing a cartilage element in situ using the reconstructive structure and reconstructing a joint having two bones separated by cartilage material.
Researchers in the surgical arts have been working for many years to develop new techniques and materials for use as grafts to replace or repair damaged or diseased tissue structures, particularly bones, cartilaginous tissue and connective tissues, such as ligaments and tendons, and to hasten fracture healing. It is very common today, for instance, for an orthopaedic surgeon to harvest a patellar tendon of autogenous or homologous origin for use as a replacement for a torn cruciate ligament. The surgical methods for such techniques are well known. Further, it has become common for surgeons to use implantable prostheses formed from plastic, metal and/or ceramic material for reconstruction or replacement of physiological structures.
It has been reported that compositions comprising the submucosa of the intestine of warm-blooded vertebrates can be used as tissue graft materials in sheet form. See U.S. Pat. No. 4,902,508. The preferred sheet compositions described and claimed in that patent are characterized by excellent mechanical properties, including high compliance, a high burst pressure point, and an effective porosity index which allowed such compositions to be used beneficially for vascular graft constructs.
The graft materials disclosed in that patent are also useful in tendon and ligament replacement applications as described in U.S. Pat. No. 5,281,422. When used in such applications the graft constructs appear to serve as a matrix for the growth of the tissues replaced by the graft constructs. When used in cruciate ligament replacement experiments not only does the portion of the graft traversing the joint become vascularized and actually grow to look and function like the original ligament, but the portion of the graft in the femoral and tibial bone tunnels rapidly incorporates into and promotes development of the cortical and cancellous bone in those tunnels. It was believed that such properties derived from the sheet structures of the intestinal tissue derived graft constructs. U.S. Pat. No. 5,281,422 also describes in FIGS. 8 and 9 doubling the graft back over itself, one layer on top of the other or rolling it concentrically, one layer on top of the other.
An advantage of the intestinal submucosa graft formed for surgical repair is its resistance to infection. The intestinal graft material, fully described in the aforesaid patents, have high infection resistance, long shelf life and storage characteristics. It has been found that xenogeneic intestinal submucosa is compatible with hosts following implantation as vascular grafts, ligaments and tendons and is not recognized by the hosts' immune system as "foreign" and therefore is not rejected.
As described in U.S. Pat. No. 5,275,826, fluidized intestinal submucosa can be injected into host tissues in need of repair, for example, bone and soft tissue such as muscle and connective tissues. Also described is the surgical reconstruction of a collagenous meniscus at the interface of articulating bones. In such reconstruction a sheet of a first tissue graft composition, preferably itself comprising intestinal submucosa of a warm-blooded vertebrate, is formed into a sealed pouch and filled with the fluidized tissue graft composition of intestinal submucosa.
The present invention is directed to multi-layered tissue graft constructs and a method of preparing those graft constructs. The intestinal submucosa tissue graft constructs of the present invention are utilized in the reconstruction of damaged or diseased cartilaginous structures. In one embodiment, a method is provided for the in vivo reconstruction of a cartilaginous structure, or for the reconstruction of a joint having two bones separated by cartilaginous material.
The method of repairing damaged or diseased cartilaginous structure in vivo is achieved by a reconstructive tissue graft structure or construct that includes a plurality of superimposed layers of intestinal submucosa tissue compressed and secured together and shaped to provide a solid multi-layer reconstructive element of the anatomical shape of the cartilaginous element to be reconstructed. The reconstructed structure is formed by superimposing a plurality of layers of small intestinal submucosa and securing the layers to one another. In one embodiment, the superimposed layers are compressed and secured together. The compressed and secured solid multi-layered structure is cut, and optionally sculptured, to form a reconstructive structure having the anatomical shape of the cartilaginous structure to be replaced.
The superimposed layers may be formed by wrapping a continuous piece of small intestinal submucosa about a pair of spaced mandrels. Preferably, the mandrels are positioned to diverge at an acute angle from an apex. This allows the concave edge of the small intestine submucosa to be closer to the apex than the concave edge and therefore compensate for the varying edge length of the small intestine submucosa. This results in a substantially planar structure of the multi-layers. Alternatively, small intestine submucosa is cut into sheets and the sheets are superimposed or stacked. The angular orientation of the sheets in parallel plane may be varied.
A clamp or other tool or hydraulic press may be used to compress the superimposed layers together and hold them while they are secured together. The layer may be secured together by stitching, crimping, quilting, drying or drying in a vacuum.
The clamp may include a slot which serves as a suturing guide. Also, the outline of the clamp may be used as a cutting guide. In addition to cutting the outline of the desired anatomical shape, the multi-layers may be sculptured in the cross-section to the desired anatomical shape.
The reconstructive structure just described may be used for reconstructing a cartilaginous element in situ. The method includes removing at least a portion, if not substantially all of the cartilaginous element, but leaving a seed portion, sculpting a reconstructive structure formed of plural layers of small intestine submucosa to the anatomical shape of the cartilaginous element being reconstructed, and positioning it adjacent to the seed portion of the cartilaginous element. The reconstructive element is secured to the seed portion of the cartilaginous element such that the reconstructive structure forms the substrate for endogenous cartilage growth from the seed portion.
A method for reconstructing a joint having two bones separated by a cartilaginous material includes removing any remaining portion of the cartilaginous material down to a bleeding bone site. A reconstructive structure formed of small intestine submucosa is positioned adjacent to the bleeding bone site and secured to the bleeding bone site so that the reconstructive structure forms a substrate for cartilaginous growth from the bleeding bone site. This provides a cartilaginous layer of material on the bone site. As an alternative, a membrane or barrier may be inserted to cover the area of the bleeding bone and the reconstructive element may be affixed to the membrane or barrier.
If a sufficient amount of cartilaginous material remains on the bone, the cartilage can be abraded to create a uniform defect without taking it to the bleeding bone. A reconstructive element is then attached to the remaining cartilaginous material.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.